As Teen tease Karen Jackson in Channel 4's black comedy Shameless, she is a lusty Lolita who gets what she wants by using sex.

But away from the infamous Jockey pub where she pulls pints for Frank Gallagher and his chavtastic family, actress Rebecca Atkinson couldn't be more unlike her on-screen character if she tried.

In real life, the pretty blonde has been dating her childhood sweetheart for eight years and is such a good Catholic girl she refuses to move in with him until she has an engagement ring on her finger.

Rebecca, 24, lives with her mum Pauline and dad Stan in Salford, Greater Manchester, just around the corner from her long-time love Tom McGarva, 24, who also lives with his parents.

In the famously flighty world of showbiz, where young actresses seem to swap partners more often than their shoes, Rebecca's goodgirl principles make a refreshing change.

She says: "Tom and I have been going out since we were at school at 16, and he's my only boyfriend.

"We're both Catholics and that's what stops us moving in together. I'd like things to be a bit more proper before we do that. I doubt I'll wait till we're married, but definitely do want to be engaged before we make that commitment."

Only one slight problem seems to stand in the way of Rebecca's romantic plans - journalism student Tom hasn't yet proposed. Rebecca secretly suspects it's only a matter of time.

"I think we will marry - at least I hope so," she laughs. "I don't wish to be with anyone else, and neither does Tom. But we're still really young and both have so many things we still want to do, so maybe we'll think more seriously about it in a couple of years."

In Rebecca's eyes, no other man compares to Tom, despite the fact she's worked alongside Shameless hunks like James McAvoy and Aaron McClusker, who plays her bad-boy bridegroom Jamie Maguire.

She explains: "I still fancy Tom like mad af ter all these years together - he's a gorgeous looking guy.

"And he understands me better than anyone else. We've known each other since we were 11 and were in the same classes at school so he knows exactly how to handle me.

"Although we've got masses in common he's the complete opposite to me so we complement each other. I can be quite highly-strung and am easily irritated because I want everything to be perfect.

"But he's so laid back and relaxed about life so he just lets me go off on one. It's nice that he lets me do that, and he helps calm me down.

"He's in no way a jealous boyfriend. We would have had real problems if he'd ever felt the need to question me, considering all the raunchy things my character gets up to."

Rebecca has a point.

Since the first series of Shameless, which returned to our screens last night, her lollipop-licking character has followed in the footsteps of her nymphomaniac mother Sheila by sleeping her way around the council estate and has even seduced her boyfriend's dad, Frank Gallagher. The sex scenes were a toe-curling torture for the young actress in her first major role since training as a dancer and landing small roles in Life On Mars, Heartbeat and Holby City.

Rebecca says: "Those sex scenes were so embarrassing at first. You feel so vulnerable when you're topless in front of a camera.

"It's overwhelming at first when the camera's on you and the crew are all around because Shameless is my first experience of doing anything like that.

"The worst one was when Karen tried to seduce Frank when he walked in on her naked in the bath.

"All the way through that scene I was so nervy and worried like mad about who was looking at me and what they were thinking of me.

"But David Threlfall, who plays Frank, is such a good teacher he did everything he could to put me at ease. And the producers make sure that when I'm doing anything in the nude we work on a closed set, and the crew all looked at the monitor and not me.

"Now it's much easier and I just get on with it. I've learned to switch into Karen's character, drop the dressing gown and do the scene, grab the gown as soon as it's over and become myself again." At the end of the last series, Karen married jailbird Jamie Maguire and viewers saw a new, sensitive side of the tart without a heart.

Before working on this new fifth series - which is based on writer Paul Abbott's real family - Rebecca undertook a huge challenge of her own, the London Marathon.

She was inspired to tackle the gruelling 26 miles by the death of her friend Milton Styles, who died of oesophagus cancer in September aged 38.

Her run raised money for the Christie Hospital in Manchester, one of Europe's largest cancer treatment and research centres. Now she plans to run it again this year.

Rebecca says: "Seeing the pain Milton endured in his final days was horrendous. His wife Julie is my neighbour and running partner, and is absolutely devastated.

"Milton was a healthy, fit young man who used to coach all the local football teams before doctors diagnosed cancer two years ago.

"He thought he had heartburn at first, and had problems keeping his food down. When doctors diagnosed cancer, I kept thinking, 'He'll be all right'.

"I couldn't believe someone so young would die of the disease. In the last 10 weeks of his life he deteriorated dramatically. He found it impossible to keep food down so suffered malnutrition.

It was so hard for Julie to see her husband so ill - she felt utterly helpless. I can't imagine how much his two kids and stepchildren miss him." Cancer is a cause that is close to Rebecca's heart, since it claimed the lives of her grandad and uncle.

"Statistics show that one in three people will get cancer. So when I'm in a room with my mum and dad, it struck me that it's likely to happen to one of us. That's a heart-breaking fact and enough to get me pulling on my trainers to help raise money.

"I'll be thinking of Milton, grandad and my Uncle Alan with each step."

Rebecca follows a punishing training regime, which sees her run 23 miles one day, six miles and an exhausting spinning class the next, coupled with countless trips to the gym to lift weights.

She hopes to run all the way, without any walking breaks, and is aiming to beat last year's time of just under four hours.

"As soon as I finished the race I had to dash up to Manchester for the start of filming of this series.

"So if you see Karen on screen walking funny, it's more to do with my blisters and chaffing than anything rude she's been up to, I promise!"

Shameless, Ch4 Tuesday nights.

CHATSWORTH CHAT: TOP SHAMELESS LINES

"You hit me in the face with a pan of porridge, I went to casualty looking like Ann Widdecombe."

Frank to Monica

"If you're really serious about him, maybe you should think about putting your name down early for a council flat."

Monica to Debbie

"Who are you? One of Tony Blair's little Thought Police? Monitoring the behaviour of your parents so you can report them to Esther Rantzen?"

Frank to Debbie Carl:

Mum, how do you spell emphysema?

Monica:

What's that you got?

Carl:

A sick note "I BET I'm the only bloke who has to cope with the fact that the only lezza he'll ever get his hands on is his ex-wife."

Frank Mimi:

What are you looking at?

Carol:

Well, I don't rightly know but it's bloody ugly and it seems to be looking back.